1. Field of the Invention
The present invention relates to a slicing machine, especially an internal diameter slicing machine which successively slices a workpiece such as a single-crystal semiconductor ingot into wafers of a predetermined thickness by means of a circular-shaped internal rotary blade.
2. Background Art
Slicing machines used for cutting a block into slices, especially cutting a single-crystal semiconductor ingot in the form of a bar into wafers, generally comprise a feed-table to carry the bar to be sliced by the blade. The feed-table carrying the bar moves in the horizontal direction for cutting and then moves upward against the blade during cutting. This blade has a cutting edge formed along the inner-edge thereof.
For producing a wafer having a flat surface, it is important to control the position of the cutting edge of the blade during the slicing process. Therefore, a deviation detecting and correcting means have been required for slicing the bar with high accuracy.
In Japanese Patent Application KOKAI number HEI3-121769, there is disclosed for example, a slicing machine having: a detecting means for detecting a deviation of the blade in the width direction of the blade i.e., in the horizontal direction of the workpiece to be sliced; at least one pair of magnetic force generating means distributed to each side of the blade and generating magnetic forces extending toward the blade; and control means operably connected to the detecting means and the magnetic force generating means for measuring the intensity of a magnetic force applied on the blade for controlling the intensity of the magnetic force such that the cutting edge of the blade is positioned in the correct cutting position.
However, the detecting means of the above described conventional slicing machine is fixed at a point at the beginning of the slicing process and/or at a point at the end of the slicing process, therefore, it is difficult to directly measure the position of the cutting edge of the blade in the workpiece. Thus the cutting accuracy of the conventional slicing machine is still not satisfactory because the deviation detecting and correcting means may put the cutting edge in the wrong orientation by detecting vibrations or curvature in the blade's surface.